In a conventional chip (IC) for communication, a S-ATA method is used in a case of near distance, and an LVDS (Low Voltage Differential Signaling) method is used in a case of short distance, and a TMDS (Transition Minimized Differential Signaling) method is used in a case of middle distance.
The LVDS is a circuit for serially transmitting data in a low amplitude differential signaling method using electric potential difference between both ends of a resistance. The LVDS is a method for transmitting digital information through a copper cable to a flat panel display (TFT-LCD) at a high speed in a method suitable for high-frequency transmission. In other words, the LVDS is a transmission method for transmitting digital information to the flat panel display through the copper cable at high speed. In the term ‘LVDS’, ‘LV’ means a low voltage. That is, it means that the LVDS uses 3.3 or 1.5V instead of a standard voltage of 5V. The LVDS has been widely used in a laptop computer because it uses less cables between a motherboard and a panel. It has been widely used between image scaler and panel of many stand-alone flat panel displays. The LVDS transmits serial data at the maximum speed of 1 Gbps. The low voltage signal swing and current mode driver voltage output cause very low noise and require low power consumption that is almost constant at any frequency. In addition, differential data transmission used in the LVDS is less affected by common mode noise. The technology has been developed to provide high-speed data transmission function to various communication infrastructure applications such as a base station, household appliances such as a switch, an add/erase multiplexer and a set-top box, a home/commercial image link, a medical ultrasonic imaging and a digital copier. In addition, the technology provides flexibility of system division.
The LVDS provides a flexible architecture in which a system designer can arrange analog/digital signal processing block on an additional board and transmit digitized data from an analog/digital (A/D) converter through a cable or a rear surface.
Digital Visual Interface (DVI) or High Definition Multimedia Interface (HDMI) uses a digital transmission protocol such as a TMDS (Transition minimized differential signaling) link. Accordingly, signal conversion chipsets such as a TMDS transmitter or a TMDS receiver of a TMDS link type are required to support the DVI. The link has been developed by Silicon Image Inc. of U.S. and became a worldwide standard. It can transmit digital data from a graphic card to a monitor by including a transmitter at the graphic card and a receiver at the monitor. An object of the TMDS link is to convert digital data output from a PC into a signal that can be transmitted to the more far distance in the higher band through the longer cable without signal loss. That is the reason that the digital signal outputted directly from the PC is weak and thus cannot be transmitted to a long distance. When a PC is close to a monitor just like a notebook, digital signal have been transmitted between the PC and monitor by using the LVDS method. However, according to the method, the transmission distance is 5 m at maximum. Accordingly, the method is impossible to transmit the digital signal to the relatively long distance, for example the distance between a desktop PC and a monitor. Thus, the new method, that is, the TMDS link method has been developed. The TMDS can be operated at 165 MHz. A single 10-bit TMDS link has a bandwidth of 1.65 Gbps and thus the link can operate in the speed when a digital image signal of 1920×1080 resolution is transmitted at 60 Hz.
The difference between the methods is based on the distance between transmitting and receiving ends. Each transmission method uses a serial method in common. Development of the methods have increased the transmission speed of multimedia data between a hard drive and a mother board, a laptop PC body and an LCD monitor, and from a desktop PC body and an LCD monitor.
However, in the platforms using the transmission methods, the transmission speed are increased more or less but there is almost no difference from the conventional method in noise caused by environments such as electromagnetic wave (EMI) and disturbance, resolution and a simple transmission line. In addition, there have been many problems that the conventional transmission method could not have solved in cases where only monitors are connected to a server without several PCs, and data in the PC body is transmitted to the monitor from very far distance or the PC body or monitor is remotely controlled.
There has been proposed a method using an optical cable to solve the problems occurring in the long distance transmission. When the optical cable is used, it is possible to solve problems such as the long distance data transmission and electromagnetic wave (EMI).
FIGS. 1a and 1b show examples of transmitting and receiving ends of an optical transmission IC using a conventional optical cable.
FIG. 1a shows the transmitting end of the conventional optical transmission IC. A reference number 11 indicates an image card of a personal computer body, a reference number 12 indicates a camera and a reference number 13 indicates a set-top box. In addition, a reference number 14 indicates a transmission chip, which includes a parallel/serial conversion logic 14a converting parallel data into serial data and a drive logic 14b performing optical transmission of the converted serial data.
A reference number 15 indicates an optical transmission drive unit including a plurality of VCSEL drive ICs generating inputted TMDS/LVDS format serial data into an analog optical signal, and a reference number 16 indicates an optical signal generator generating an optical signal by interlocking with the optical transmission drive unit 15, transmitting the signal to an optical cable (a plastic optical cable of 250 μm or a glass optical cable of 62.5 μm). In addition, the optical signal generator 16 includes a plurality of optical signal generating elements.
A reference number 17 indicates a logic IC transmitting DDC data generated from the set-top box 13, interfacing the DDC data transmitted from a receiving end to the set-top box 13. A reference number 18 indicates a DDC data drive unit generating the DDC data into an analog optical signal or converting a received analog signal into an electrical signal. The DDC data driving unit 18 includes a VCSEL drive IC 18a generating DDC data into an analog optical signal, transmitting the signal and a photodiode receiver IC 18b converting a converted electrical signal into DDC data.
A reference number 19 indicates an optical signal generator and receiver transmitting an optical signal to an optical cable by operating with the DDC data drive unit 18 or receiving an optical signal transmitted from the optical cable. The optical signal generator and receiver includes an optical signal generator 19a generating an optical signal by operating with the VCSEL drive IC 18a and an optical signal receiver 19b receiving an optical signal transmitted from the optical cable.
FIG. 1b shows a receiving end of a conventional optical transmission IC. A reference number 21 indicates an optical signal receiver receiving an optical signal transmitted through an optical cable (a plastic optical cable of 250 μm or a glass optical cable of 62.5 μm) and the optical signal receiver 21 includes a plurality of optical signal receiving elements.
A reference number 22 indicates a photodiode receiver converting a signal received from the optical signal receiver 21 into TMDS/LVDS format non-serial data, which includes a plurality of photodiode receiver ICs.
A reference 23 indicates an optical signal receiver and generator receiving an optical signal transmitted from the optical signal receiver 21 or converting DDC data into an optical signal, transmitting the signal to the optical cable. The optical signal receiver and generator includes an optical signal receiver 23a receiving the optical signal transmitted from the optical cable and an optical signal generator 23b generating an optical signal and transmitting the signal to an optical cable.
A reference number 25 indicates a logic IC receiving the DDC data generated from the set-top box and transmitting the DDC data to the set-top box. A reference number 26 indicates a receiving IC, which includes a receiving logic 26a receiving TDMS/LVDS format data converted into an electrical signal and a non-serial logic 26b converting the TMDS/LVDS format data received from the receiving logic 26a into TTL data of Dec. 24, 1948 bit, transmitting the converted TTL data to a TFT-LCD panel 27 or a PDP panel 28.
ICs for using the conventional cable are used to transmit only video and audio signals of PC, HDTV, etc. Accordingly, the ICs cannot be used in various fields and can be used in limited fields such as a PC body and an LCD monitor (PDP monitor) as shown in FIGS. 1a and 1b. 
Accordingly, usability of expensive IC and cable is restricted to the limited fields.
In addition, the conventional optical transmission IC for a specific use is designed not to interrelate with LVDS or TMDS mode, and so limitedly used to characteristics of media, transmission distance and so on.